The present invention relates to packer and bridge plug type tools used in wellbores and more particularly to limiter assemblies, which resist extrusion of packer elements when exposed to borehole conditions, especially high pressure and high temperature.
In the drilling or reworking of oil wells, a great variety of downhole tools are used. For example, but not by way of limitation, it is often desirable to seal tubing or other pipe in the casing of the well, such as when it is desired to pump cement or other slurry down the tubing and force the cement or slurry around the annulus of the tubing or out into a formation. It then becomes necessary to seal the tubing with respect to the well casing and to prevent the fluid pressure of the slurry from lifting the tubing out of the well or for otherwise isolating specific zones in a well. Downhole tools referred to as packers and bridge plugs are designed for these general purposes and are well known in the art of producing oil and gas.
Packers generally rely on a packer sealing assemblies to seal the wellbore. Traditionally such assemblies are comprised of at least one elastomeric sealing element and at least one mechanically set slip. Typically, a setting tool is run in with the packer to set it. The setting can be accomplished hydraulically due to relative movement created by the setting tool when subjected to applied pressure. This relative movement causes the slips to ride up on cones or wedges and extended into biting engagement with the surrounding casing or wellbore. At the same time, the sealing element is compressed into sealing contact with the surrounding casing or wellbore.
Packer element back-up shoes and rings have been employed to support the ends of the packer sealing elements as the elements are expanded into contact with a borehole wall. These back-up shoes or rings also may limit the axial extrusion of the packer sealing elements; thus they are sometimes called limiters or extrusion limiters. The shoes are typically segmented and, when the tool is set in a well, spaces between the expanded segments have been found to allow undesirable extrusion of the backer elements, at least in high pressure and high temperature wells. This tendency to extrude effectively sets the pressure and temperature limits for any given tool. Various improvements have been developed in ongoing efforts to prevent the extrusion of the packer elements between the segmented gaps and, while some have been effective to some extent, they have been complicated and expensive.